1. Field of the Invention
The present invention relates to a method for preparing transformed plant of the family Gramineae and a method for transforming a plant of the family Gramineae.
2. Statement of the Prior Art
As a method for transforming a plant, genetic transduction utilizing Agrobacterium has been established. However, Agrobacterium fails to infect grasses of the family Gramineae and other techniques have been attempted.
As one of the techniques, direct transduction of vector DNA has been studied. For example, there is reported a method for transforming by means of electroporation, particle gun, polyethylene glycol or microinjection, that is, it is possible to transduce a gene into protoplast or callus in corns [Nature, 319, 791 (1986)], grasses [Mol. Gen. Genet., 204, 204 (1986)], wheat [Mol. Gen. Genet., 199, 178 (1985)]and pasture [Mol. Gen. Genet., 199, 178 (1985)]. In all of these methods, obtaining transgenic plant is greatly restricted by the difficulty of protoplast culture and the complicated handling. As an example where a gene is transduced to a plant, there is a report that plasmid is injected into young seedling rye by microinjection and the gene is expressed in seeds derived from the plant [Nature, 325, 274 (1986)]. However, this technique has not yet been established as a method for transducing a gene into a plant efficiently.
There is also reported a method for preparing a transformed plant using the transduction system in Gramineae by electroporation to protoplast [Japanese Patent Published Unexamined Application No. 1-18179]. In many of cereal plants, the regeneration from protoplast has not been established. In addition, many selection cultures and long periods of time are required for preparation of protoplast. It is also the actual situation that protoplast culture is applicable only to a part of the species and cultivars having excellent tissue culture property, even though they are the same crop.
A method for transformation by a laser perforation is currently utilized for transformation of an animal cell and used for preliminary experiments on plant tissues and cells [Weber et al., Plant Cell Tissue and Organ Culture, 12, 219 (1988)], and experiments on organelle [West German Patent Application 3,707,111A]. However, it is unknown to transform microspore of a plant by the method described above. There is also reported a method for preparing a transgenic plant using the gene transduction system into sweet corn embryo by a laser [Japanese Patent Published Unexamined Application No. 2-9378]. According to this method, however, the thus obtained transformant is a chimera. Any method for obtaining a transformant has not been established with respect to cereal plants.
As described above, many attempts have been made on transformation of a plant but transformation has not been yet successful for monocotyledons, especially in Gramineae, although it has been long desired.